Controller for alternating-current motors



AISIMON. CONTROLLER FOR ALTERNATING CURRENT MOTORS.

APPLICATION F ILED 056.26, 1919.

Patented Apr. 18, 1922.

ABC.

INVENTOR.

A TTORNEY UNITED STATES PATENT, orrics.

ARTHUR SIMON, OF MILWAUKEE, WISCONSIN, ASSIGNOR TO THEICTITLER-HAMMER MFG. 00., OF MILWAUKEE'WISCONSI N, A CORPORATION OF WISCONSIN.

ooNrRoLLER ron ALT'E NATIN -GURBENT MOTORS.

To all whom it may concern: 4

ARTHUR SIMON, a citi- Be it known that I zen of the United gtates, residing at Milwaukee, in the county of Milwaukee and State of Wisconsin, have invented new and useful Improvements in Controllers for Alternating-Current Motors, of which the following is a full, clear, concise, and exactdescription, reference being had to the accompanying drawing, forming a part of this specification.

This invention relates to controllers for.

alternating current motors and other power consumlng devices havlng mutual inductance.

It has been proposed to control three phasedevices of such character by means of V or open delta connected three phasetransformers, but the latter, as heretofore constructed,

inherently tend to produce phase distortion resulting, when'used for motor control, in

very serious reduction of the motor torque particularly during starting under heavy load. a, 1

The present invention has among its objects that of overcoming such tendency of transformers of the character stated.

Another object is that of providing a controller for use in the foregoing relation, including a three phase V-connected transformer wherein provision is made for maintaining for the energy transmitted thereby, substantially the phase balance of the sup ply line.

Another object is to provide an improved core member for transformers of the aforesaid and other types.

Other objects and advantages will herein-' after appear.

In the accompanying drawing, Figure 1 is afront elevational view'of a transformer illustrative of the invention, also illustrating diagrammatically certain proposed circuit connections therefor; while,

Fig. 2 is a horizontalsectional view of the same, the coils omitted.

Referring to Fig. 1 of the drawing, the same illustrates a three phase auto-transformer connected in V or open delta to sup:

ply lines. A,.B, C and adapted totransmit electrical energy therefrom to a motor M which may inpractice be of the squirrel cage or other preferred type.

Said transformer includ a magnet c and circuit connections being a Specification of Letters Patent. Pgfljnted A 18 1922 Application filed December 26,1919. Serial in. 347,253. 7 7

frame or core member 5 having parallel legs 6, 7 and 8 terminally connected by transverse upper and lower portions 9 and 10, the outer legs 6 and 8 being provided with coils 11 and 12 respectively and the center leg 7 being unwound.

A transformer frame so constructed and root of three. Hence in designing trans-H formers of this type it has been customary to make the cross :area of the center leg bear a substantlally correspondingrelation to the cross area of the outer legs, therebyprovid v mg for a substantially uniform flux density in the several legs. v

- It has, however, been determined 'practically thattheregulation effected by the trans-former is greatly improved by making the cross area of said center leg considerably less than that theoretically required, thus effecting a relatively high magnetic satura tion of said center leg and consequent increase in impedance of those components of the electromagnetic circuit of the transformer which include the center leg, relative to the impedance of thosecomponents including only the outer legs. 1 The proportion of the total'flux carried by said center :leg is thus reduced, with acorresponding relative increase in mutual inductance of the coils of the outer legs, which condition is highly favorable to the phase stabilizing tendency inherent inthewindings of the motor.

In both figures of the drawing the dotted lines associated with the center leg 7 indicate approximately the ilateral extentof said member theoretically required to give a uniform density of the effective flux in the several legs, while the full lines indicate the reduced dimension of said member calculated to provide the accentuated flux-den sity contemplated herein.

By thus proportioning the cross areas and consequentflux densities of the center to the outer legs, it has; been found possible to tegral with the center leg 7 while the outer legs 6 and S are of unreticulat ed form and hence adapted to ready assembly of the coils thereon. Said outer legs are moreover of suitable length for clamping respectively against the oppositely projecting ends of said transverse portions 9 and 10, all of said sections being composed of suitably insulated laminte.

Upper and lower clamping devices 16 and 17 serve for securement of the various core sections in assembled relation and also for mounting of the assembled transformer upon a suitable support 18.

Referring particularly to Fig. 2, each of said clamping devices comprises a pair of relatively rigid metallicstrips or bars 19 and 20 extending longitudinally of the core member and having its terminal portions up-bent and punchedto provide lugs 21 and 22, and a pair of relatively short transverse bars 23 and 24 similarly provided with lugs adapted to be secured to the corresponding lugsof the bars 19 and 20 by means of bolts In practice the several bars may preferably be of such relative lengths and contour as to render the various pairs of cooperating lugs slightly divergent from their outer ends inwardly, whereby upon tightenin." the bolts 25 a strong clamping action is eflected both for forcing and holding the outer core sections against the end portions of the central section and also for main taining the respective upper and lower portions of the laminae in suitable contact.

The central portions of the laminae may be clamped in suitable contact by means of rivets 26 extending transversely through the respective core sections, or otherwise.

Each of the lugs 21 of the upper and lower elongated clamping bars 19 is furthermore extended to provide terminally located feet 27 for moruiting of the transformer upon the support 18.

Although the circuit connections illus trated are those of an auto-transformer it is to be understood that all of the foregoing features are equally applicable to, pure induction transformers.

Vhat I claim as new and desire to secure by Letters Patent is:

'1. In an alternating current controller. thecombination with a power consuming device whose operation is characterized by mutual inductance, of a transformerto supply electrical energy thereto, said transformer comprising a magnetic frame having spaced legs and an intermediate leg, said spaced legs carrying respectively V-con nected coils adaptedto-mutually inductive action and said intermediate leg being proportioned with reference to said spaced legs to increase the mutual inductance of said coils.

2. In an alternating current controller, the combination with a power consuming device having an inherent tendency against phase distortion of its circuit, of an energy supplying transformer comprising'a pair of coils connected in open delta to a three phase supply circuit and a magnetic frame having siaced legs carrying said coils respectively in a relation of mutual inductance and an intermediate leg adapted to carry a portion of the flu induced by each of said coils, said legs being relatively proportioned to accentuate the mutual inductance of said coils for supporting such tendency of said power consuming device.

8. In an alternating current controller, the combination with a power consuming device having an inherent tendency against phas distortion of its circuit, of an energy supply ing transformer comprising a pair of coils connected in open delta to a three phase supply circuit and a magnetic frame having spaced legs carrying said coils respectively in a relation of mutual inductance and an intermediate leg adapted to carry a portion of the flux induced by each of said coils, the cross area of said intermediate leg being so related to the cross areas of said spaced legs as to reduce the proportion of the total effective flux carried by the former for supporting such tendency of said power consuming device.

l-J A three phase alternating current transformer comprising a magnetic frame having a center leg and a pair of outer legs, and open delta connected coils carried by said outer legs respectively, said center leg and said outer legs being proportioned to accentuate the flux density of the former.

5. A three phase alternating current transformer comprising a magnetic frame having a center leg and a pair of outer legs, and open delta connected coils carried by said outer legs respectively, said center leg and said outer legs being proportioned to accentuate the mutal inductance of said coils.

6. A three phase alternating current transformer comprising a magnetic frame having a center leg and a pair of outer legs, and open delta connected coils carried by said outer legs respectively, said center leg and said outer legs being proportioned to render the flux density of the former higher than that of the latter for accentuating the mutual inductance of said coils.

7. A three phase alternating current transformer comprising a magnetic frame having three associatedlegs, two ofsaid legs having electromagnetic coils connected in open delta and the third leg being arranged to carry a portion of the flux induced by said coils, the cross areas of said legs being proportioned to increase the flux density of said third leg for decreasing the proportion of the total effective flux carried thereby. g

8. An alternating current transformer comprising a frame having three magnetically connected legs, a pair of electromagnetic coils connected in open delta to a three phase supply circuit associated with the legs of said frame to cause two of said legs to act in a relation of mutual inductance and the third leg to carry a portion of the flux induced by each of said coils, said third leg being so proportioned with respect to said other legs as to increase the impedance of those components of the electromagnetic cir- I cuit of the transformer which include the center leg, relative to the impedance of the components including only the outer legs.

9. A three phase alternating current transformer comprising a magnetic frame having a pair of spaced coil-carrying legs and an intermediate leg, the coils of said spaced legs being connected in open delta and the cross area of said intermediate leg being greater than that of either of said spaced legs, but less than the product of the cross area of either of saidspaced legs times the square root of three.

In Witness whereof, I have hereunto subscribed my name.

ARTHUR SIMON. 

